If you're heading to Singapore for a business or leisure trip, you should pick up a prepaid SIM card at the airport. The best we've seen is the StarHub MaxMobile Prepaid SIM card, which we've detailed below.

But before jumping into the details of the SIM, check out the costs of using an Australian SIM card in global roaming mode -- it really is something to be avoided.

The high cost of global roaming in Singapore

Optus charges $20 per megabyte of internet usage, Telstra $15 and Vodafone $10. That means with Optus, a standard resolution iPhone picture sent in an email would cost $42.

Calling Australia from Singapore on your mobile while roaming costs a whopping $3/min with Three, $2.35/min with Optus, $1.55/min with Telstra, 90c/min with Vodafone on the Traveller plan, or $1.08 on standard Vodafone World rates.

Receiving calls is almost as bad: $1.90/min with Vodafone on the Vodafone Traveller plan, $1.47/min with Telstra, $1.10/min with Optus, $1/min with Three, and 43c a minute with Vodafone's standard world rates.

StarHub's prepaid SIM card: a cheaper option

StarHub, a major 3G mobile network in Singapore, has the best offer for travellers: a SIM card with unlimited data usage at a very cheap price.

It comes with SGD$12 or SGD$32 of value included respectively, which can be used toward any of the plans.

If you're only in Singapore for a stop-over or a short trip, you can also buy a single day of access for SGD$4 for a low speed connection (2Mbit/s) or $6 for a higher 7.2Mbit/s connection.

Three days' access costs SGD$10/$16, and seven days costs just SGD$15, or SGD$25 if you want full speed.

If you will be making regular trips to Singapore, you can even get a 60 day plan for SGD$32, though that only includes 2.5GB of data, not unlimited.

Note: StarHub defines "unlimited" as a maximum of 2.2GB of data per day, which we think is pretty generous, as that's still one or two TV episodes and a huge amount of web and email usage each day.

Call rates

The StarHub MaxMobile Prepaid SIM does not allow voice calls to be made -- it is a data/SMS only SIM.

However, you can use Skype to make calls on an iPhone or laptop, and if you get a Skype Online Number, and leave Skype open on your phone, people can call you on a local Australian number and your mobile will ring in Singapore!

Skype is available for quite a few smartphones, including the iPhone, Nokia handsets that run the Symbian OS and Android phones. (It has also been built for Blackberry devices, but US telco Verizon has snapped up a worldwide exclusive deal on that with an unknown end date.)

Activating it

Once you've put the SIM card in your phone, you will need to activate it with a plan.

Send an SMS to 6782 with one of the following keywords, indicating your choice of plan.

Keyword

Data Plan Description

2M1H

1 Hour Plan for 2.0Mbps Speed

2M1D

1 Day Plan for 2.0Mbps Speed

2M3D

3 Day Plan for 2.0Mbps Speed

2M5D

5 Day Plan for 2.0Mbps Speed

7M1H

1 Hour Plan for 7.2Mbps Speed

7M1D

1 Day Plan for 7.2Mbps Speed

7M3D

3 Day Plan for 7.2Mbps Speed

7M5D

5 Day Plan for 7.2Mbps Speed

Topping it up

The StarHub MaxMobile Prepaid SIM card has six months' validity after the last topup -- so if you will be making several trips through Singapore, you can just buy recharge vouchers for extra days of access using any remaining balance on the card.

You options are to:

Buy a voucher at a retail outlet: The topup vouchers are called StarHub Happy Prepaid Top-Up Cards, and they're available in denominations of $6, $18 and $38 at any StarHub shop, Starhub partner outlet, 7-Elevens or Cheers Convenience Store. Once you have it, you can apply it to your account SMS to 6782 in the following format:

TOPUP [10 digit top up card] [6 digit PIN number]

Add credit online: You can use a credit card to top up your account on StarHub's website here.

Setting up your phone to work with it

To get the internet working on your phone, you'll need to change the "Access Point Name" (APN) setting in it.

Starhub's APN details are:

APN: shppd Username: (leave blank) Password: (leave blank)

To do this on an iPhone, connect the iPhone to a Wi-Fi hotspot, and in the iPhone's web browser, go to the website unlockit.co.nz. Select "custom APN", then from the drop-down list, select "SG - Starhub Prepaid". Then click "create profile" and "install".

On an Android phone, we highly recommend the Tweakker app which costs A$4.16 to download and install on your phone, but will handle the settings for you automatically.

For instructions on how to change the settings manually on an iPhone, Android-based phone, Windows Phone 7 handset, or Nokia phone, go to unlockit.co.nz.

Note: if you change the SIM card in your BlackBerry, all internet services such as email, apps and web browsing will stop working. You'll only be able to make and receive calls. This is one of the limitations of BlackBerry handsets -- the internet side of it is tied to the Australian SIM card.

Compatibility with Australian phones

The Starhub 3G network uses the 2100MHz radio frequency, and should work with all Australian mobiles and modems, including iPhone 3G/3GS/4G and iPad.